This is a really cool concept! I do have a few little gripes:
- The vertical speed feels much faster than the horizontal speed, I assume because the snake is traversing a grid made up of ASCII characters that are at least twice as tall as they are wide. Is there any way to equalize this so that it feels like you're always moving at the same speed?
- Restarting from your last item collection is fine, but in the demo it often means you have to track back through a long section to return to the hub area, with any death forcing you to restart from the same distant checkpoint. I'd consider letting players reactivate old checkpoints to remove some of that friction. Alternatively, you could Dark-souls-ify the level designs so that following a seemingly divergent path will most often lead you immediately back to a hub area once it's been completed. I think that might be the best option, as backtracking isn't fun if the areas have been fully explored.